Tuesday, October 30, 2012

Dolly Parton and the art of dieting

Sometime back in the early 1990s or thereabouts, Dolly Parton was
being interviewed by the famous BBC chat show host, Michael Parkinson. When
asked about what diet she used to keep her figure, she replied: “Honey, if you
want to lose weight, get your head out of the slop bucket”. In other word, just eat less. No truer
words were ever uttered in the vast realm of advice on dieting. This year we
have seen a number of scientific papers published on sugar sweetened beverages,
some designed to boost weight gain and some designed to induce weight loss, all
adding to the belief that sugar sweetened beverages are both the cause and the
cure for modern obesity. A recent paper from the Department of Nutrition at
Harvard will help put things in perspective, but only for those wishing to have
an accurate perspective.

The first [1] of the sugar
papers looked at four groups each given 1-liter of a beverage per day for 6
months. Group 1 receiver a liter of regular sugar sweetened Coke. Group 2 were
given a liter of semi-skimmed milk with an approximate equal calorie level to
the Coke. Groups 3 and 4 respectively received 1 liter of diet Coke or water.
According to the authors, the consumption of the energy-containing beverages
led to a compensation effect with a reduction in the intake of other foods and
no overall change in energy intake. No dietary data are provided in the paper
but 1 liter of regular Coke would have diluted out its equivalent caloric value
from all other foods, leading to a reduction in the intake of the latter by 430
calories per day. This Coke group showed a significant accumulation of fat in
the liver compared to others but we will never know if it was due to the
absurdly high total intake of sugars (about double the normal according to my
calculations) or to a reduction in the intakes of micro-nutrients associated
with 430 less food than normal every day. Coke for example, does not contain, the
B-vitamin riboflavin, but low riboflavin status will lead to increased blood
pressure, and the authors did see a rise in blood pressure with regular
Coke.

So, 1 liter of Coke per day did not lead to weight gain ( for example
a 1.3% gain with Coke and a 0.8% gain with water). However, two studies
reported in the New England Journal of Medicine show that if sugar sweetened
beverages in children are replaced with a calorie free version, then weight
loss does occur [2]. These
studies will be widely cited as evidence that sugary drinks cause obesity. In
fact, these studies simply show that if you do as Dolly Parton says, and simply
eat less, you will lose weight so the weight loss could have been with any
caloric source, not just sugar-sweetened beverages.

Which brings me to the Harvard paper [3].
This study (a subset of a larger dietary intervention) looked at how variation
in the distribution of calories in a weight loss regimen influenced weight
change and also changes in body composition. Four dietary treatments were used
and an energy deficit of 750 kcal per day was the target for each participant.
The diets varied the level of fat, protein and carbohydrate. At 6 months, the
average amount of fat lost was 4.2 kg and the loss of lean tissue was 2.1
kg. About half of this fat loss
was due to loss of fat from the abdominal fat with about a third lost from
subcutaneous fat. Only 0.1 kg of fat was lost from the liver but this
represented a loss of 16% of liver fat. There were no differences in any of
these measures according to the composition of the weight reduction diets,
again, upholding the Dolly Parton rule.

In summary, the first study tells us that if you oblige subjects to
eat a 1-liter bottle of regular Coke every day, you won’t gain weight because
you reduce your intake of other foods keeping energy intake constant. The
second tells us that extracting calories from children’s diets will lead to a
weight loss, in this case using sugar sweetened beverages as the target food.
The third tells us that Dolly Parton was correct. It really doesn’t matter what
the composition of your weight reducing diet is so long as the caloric
restriction operates.

So for what its worth, here are my basic rules about successful
dieting:

1.Never start a diet until you have though
about it long and hard given that the relapse rate of weight loss is so high.

2.Never start a diet until you have built
physical activity into your daily routine. Physical activity will reverse the
negative effects of obesity such as poor glucose management, higher blood
pressure and elevated blood lipids.

3.Don’t diet on your own. Join a weight loss
group and get the benefit of the social network of dieting and maintaining
weight loss.

4.Heed Dolly Parton and just eat less and
eat according to your preferences

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About Me

I graduated from University College Dublin in 1971 with an Masters in Agricultural Chemistry, took a PhD at Sydney University in 1976 and joined the University of Southampton Medical School as a lecturer in human nutrition in 1977. In 1984 I returned to Ireland to take up a post at the Department of Clinical Medicine Trinity College Dublin and was appointed as professor of human nutrition. In 2006 I left Trinity and moved to University College Dublin as Director of the UCD Institute of Food and Health. I am a former President of the Nutrition Society and I've served on several EU and UN committees on nutrition and Health. I have published over 250+ peer reviewed scientific papers in Public Health Nutrition and Molecular Nutrition (seehttp://www.ucd.ie/foodandhealth/people/managementteam/profmikegibney/) and am principal investigator on several national and EU projects (www.ucd.ie/jingo & www.food4me.org)